Fix listener setup for when the parent change is staged or integrating

An old bug that went unnoticed for a long time appeared again following the rollout of the waterfall model of cherry-picking. If the target parent of a proposed cherry-pick (on the source branch) is still running in CI, the bot would set up a listener event for merge_ and abandon_ for the proposed parent, but these listeners were never updated to pass the necessary parameters to take action if the event was received.

In the current architecture, listening for merge_ is unnecessary since we're expecting the parent to perform a pick, creating a cherryPickCreated_ type event which is already handled. The abandon_ listener setup needs to be updated